Blended Polyphosphazene/Polyacrylonitrile Membranes for Direct Methanol Fuel Cells

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Abstract
Direct liquid methanol fuel cell tests were performed with membrane electrode assemblies (MEAs) fabricated with polyphosphazene-based proton-exchange membranes. The membranes were prepared from sulfonated poly[bis(3-methylphenoxy)phosphazene] that was blended with polyacrylonitrile and then UV cross-linked using benzophenone as the photoinitiator. MEAs worked best when a high ion-exchange capacity (high conductivity) polyphosphazene membrane contacted the electrodes, in which case the fuel cell power output was nearly the same as that with Nafion 117 (for current densities but the methanol crossover was three times lower than that of Nafion. With a three-membrane composite MEA (a methanol-blocking film sandwiched between two high conductivity membranes), there was a significant decrease in crossover (ten times lower than that of Nafion 117) with a modest decrease in current-voltage behavior. © 2002 The Electrochemical Society. All rights reserved.